1. Field of the Invention
This invention relates to portable power tools and, more particularly, to a control for operating a power source on the power tool.
2. Background Art
There are many hand-holdable power tools available on the market today. With those tools having dangerous working/operating elements, it is common to incorporate safety features which require that the user's hands both be strategically placed to avoid potentially injurious contact with the particular operating elements.
One such tool is a hedge trimmer of the type utilizing a cantilevered, forwardly projecting cutting assembly. An exemplary cutting assembly uses reciprocating blades which are configured and synchronized to produce a scissors action that severs vegetation. In one form, a gas operated power source drives the cutting assembly. A rear handle is provided on the power unit to support the rear of the tool. A forward handle is provided nearer the cutting assembly. By gripping both handles, the user can maintain the tool in a balanced cutting position.
It is also known to use a U-shaped forward handle, commonly called a "D-handle", on the tool. This allows the user to grip at least three different regions which facilitate left- and right-hand vertical trimming and horizontal trimming.
Because of the close proximity of the forward handle to the cutting assembly, it is known to incorporate a safety power cutoff switch. In one form, this safety switch is controlled by an actuator bar that is pivotable between an "on" position and a "disable" position. The bar is normally biased to the disable position. By drawing the bar towards the forward handle, the operator can reposition the bar to the on position and maintain the bar in that position by a natural gripping action on the handle which squeezes the bar thereagainst. The user is thus required to grip the forward handle and bar with the forwardmost hand, thereby isolating this hand from the cutting assembly.
In some constructions, the bar is designed to be comfortably grasped with the handle only with the user grasping the handle for horizontal cutting. While it is possible to reposition the bar to the on position while using the left- and right-hand vertical grips, the user does not have the same leverage. Accordingly, the grip may be relatively uncomfortable and may ultimately cause user fatigue.
A more serious problem that this presents is that the user, in order to avoid this discomfort and/or fatigue, may defeat the safety feature by mechanically securing the bar to the handle so that it is always in the "on" position. The user's front hand is then unconstrained during operation and may be inadvertently brought into contact with the cutting assembly.